One of the most frustrating parts of looking for clinical trials is finding one that seems perfect — and then not being sure whether you actually qualify. Eligibility criteria can read like a technical checklist, and it's hard to know when a factor disqualifies you and when it's just a preference.
Here's how to approach eligibility, what the most common criteria mean, and what to do when you're on the fence.
What Eligibility Criteria Are
Every clinical trial has two types of eligibility criteria:
Inclusion criteria are the requirements you must meet to participate. Things like a specific diagnosis, being within a certain age range, or having received (or not received) prior treatments.
Exclusion criteria are factors that prevent you from participating. These might include other medical conditions, medications you're currently taking, recent surgeries, or lab values outside a certain range.
These criteria aren't arbitrary — they're designed to ensure that the results apply to a specific population, and to protect participants whose health might make the experimental treatment risky.
The Most Common Criteria You'll See
Diagnosis and disease stage. Most trials are specific about what counts as a qualifying diagnosis. A breast cancer trial might specify "HER2-positive, locally advanced or metastatic." A diabetes trial might require a specific HbA1c range. Your diagnosis paperwork and any recent lab results will help you evaluate this.
Age range. Trials almost always specify an age range. Pediatric trials recruit children and teens. Most adult trials set a minimum age of 18. Some specify upper limits based on the population researchers want to study.
Prior treatment history. This is one of the trickiest criteria. Some trials require that you've already tried standard treatments and they haven't worked. Others exclude you if you've received a specific drug or therapy before. Knowing your treatment history in detail is essential.
Current medications. Certain drugs interact with experimental treatments or could confound the results. Trials commonly exclude people taking anticoagulants, certain immunosuppressants, or other drugs being studied. Sometimes switching medications makes you eligible — but only after a washout period.
Lab values and organ function. Trials often specify minimum kidney function, liver enzyme levels, blood counts, or other markers. These protect participants from receiving a drug their body isn't able to process safely.
ECOG Performance Status. For cancer trials especially, you'll often see a reference to ECOG score — a 0-to-4 scale that measures how well a patient can carry out daily activities. Most trials accept participants with a score of 0 or 1 (fully active or slightly restricted). If you see this, ask your oncologist what your score is.
What to Do When You're Not Sure
Don't self-disqualify. The most common mistake patients make is reading a criterion, deciding they don't meet it, and moving on. Research coordinators handle ambiguous situations every day. Call and describe your situation — they can often tell you in minutes whether you'd be screened in or out.
Have your records ready. When you call a study site, having your diagnosis documentation, recent labs, and medication list in front of you speeds the conversation considerably.
Ask about exceptions. Some criteria have waivers or sponsor-approved exceptions for edge cases. You'll never know unless you ask.
Check multiple trials. Criteria vary significantly from trial to trial, even for the same condition. If you don't qualify for one, you might qualify for another. Don't treat a single rejection as the final word.
When You're Disqualified
Disqualification happens, and it's not personal — it's about scientific validity and your safety. If you don't qualify for a trial you were interested in, ask the coordinator:
- Why specifically you don't meet the criteria
- Whether that factor could change (e.g., stopping a medication, waiting a period of time)
- Whether they're aware of other trials you might be a better fit for
Research coordinators are often familiar with trials at other institutions and may point you somewhere helpful.
The Fastest Way to Find Out
The fastest way to know if you qualify is to search, find trials that look like a match, and make the call. Most research teams will pre-screen you over the phone in 10 to 15 minutes before you ever come in for a formal screening visit.
Search TrialFinder by your condition and location to find recruiting trials near you. Each result links to the full eligibility criteria so you can review before reaching out.